In recent years, as a compression encoding scheme of moving image data, various schemes have been proposed and standardized. Furthermore, the compression encoding scheme is applied to wide usages from a low speed/low quality moving image of a video telephone of a cellular phone or a smart phone to a high quality moving image with large capacity of hi-vision television broadcasting, and is commercially used.
Meanwhile, for example, in a scheme of emphasizing low delay than image quality of a video conference system or a monitoring camera, for example, image encoding (low delay encoding) is performed based on a gradual decoder refresh (GDR) scheme.
In the GDR, for example, since serialization delay in a low speed link may cause arrival delay of a packet of an I (Intra-coded: Intra) frame or packet discard, intra-image data is divided into a plurality of frames (pictures) for transmission.
In addition, a GDR frame includes an intra-macroblock part (intra-slice: Intra-slice) and a predicted macroblock part (inter-slice: Inter-slice). Furthermore, when all GDR frames have been received, a decoder can completely refresh an image.
As described above, for example, in a video conference system or a monitoring camera, low delay encoding is realized based on the GDR scheme. Herein, encoding based on intra-prediction is limited to a part of an image, and shows a tendency to an increase in an information amount.
Although the intra has been limited to a part, when encoding is performed from an upper side to a lower side an image, for example, it may exceed an upper limit (a target information amount) of an information amount due to a communication speed.
As described above, when an information amount of an encoding result exceeds the target information amount, since the information is discarded or an intra-information amount is thinned out, resulting in the degradation of image quality.
By the way, in the past, various image encoding apparatuses, image encoding methods, and image encoding programs have been proposed.
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